A journalist named Johnny Barrett, determined to win a Pulitzer Prize, feigns insanity to get committed to a mental institution. His objective is to solve a patient's murder that occurred within the facility. Guided by his editor and with the reluctant support of his girlfriend, Barrett undergoes extensive training to convincingly play the part of a deranged man. Once admitted, Barrett meets a variety of patients, each with unique psychological conditions, shedding light on the grim realities of life inside a psychiatric ward.

As Barrett delves deeper into the investigation, he encounters a trio of key inmates: a former soldier suffering from delusions due to his traumatic war experiences, an African-American man who believes he's a white supremacist, and a nuclear scientist who has regressed into a childlike state. Each interaction brings him closer to uncovering the truth about the murder but also pushes him further into the depths of his fabricated madness. The tension mounts as Barrett battles to maintain his sanity while continuing his dangerous charade, risking more than just his career in the process.